Uses for WSX ligands in hematopoiesis are disclosed. In particular, in
vitro and in vivo methods for stimulating hematopoiesis (e.g.,
myelopoiesis, erythropoiesis and especially, lymphopoiesis) using a WSX
ligand (e.g., anti-WSX receptor agonist antibodies or OB protein), and
optionally another cytokine, are described.